Add configuration files, database migrations, and authentication implementation scaffolding

internal/crypto/crypto.go

@@ -0,0 +1,72 @@
+package crypto
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/hmac"
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	"io"
+)
+
+// Encrypt encrypts plaintext using AES-GCM with the provided key.
+// The key must be 32 bytes (AES-256).
+func Encrypt(plaintext []byte, key []byte) ([]byte, error) {
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return nil, err
+	}
+
+	nonce := make([]byte, gcm.NonceSize())
+	if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
+		return nil, err
+	}
+
+	// Seal appends the ciphertext to the nonce, so we return [nonce][ciphertext]
+	return gcm.Seal(nonce, nonce, plaintext, nil), nil
+}
+
+// Decrypt decrypts ciphertext using AES-GCM with the provided key.
+func Decrypt(ciphertext []byte, key []byte) ([]byte, error) {
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return nil, err
+	}
+
+	nonceSize := gcm.NonceSize()
+	if len(ciphertext) < nonceSize {
+		return nil, fmt.Errorf("ciphertext too short")
+	}
+
+	nonce, actualCiphertext := ciphertext[:nonceSize], ciphertext[nonceSize:]
+	return gcm.Open(nil, nonce, actualCiphertext, nil)
+}
+
+// GenerateBlindIndex creates a deterministic HMAC-SHA256 hash of a value.
+// This allows searching for encrypted data without knowing the plaintext.
+func GenerateBlindIndex(value string, salt []byte) string {
+	h := hmac.New(sha256.New, salt)
+	h.Write([]byte(value))
+	return hex.EncodeToString(h.Sum(nil))
+}
+
+// GenerateKey generates a random 32-byte key.
+func GenerateKey() ([]byte, error) {
+	key := make([]byte, 32)
+	if _, err := io.ReadFull(rand.Reader, key); err != nil {
+		return nil, err
+	}
+	return key, nil
+}